package 笔试.神策;

import java.util.Scanner;

/**
 * @author:谢君臣
 * @Date:2021/9/8-16:03
 * @version:1.0
 * @function:
 */
public class Main02 {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int x = scanner.nextInt();
        int y = scanner.nextInt();
        int m = scanner.nextInt();
        System.out.println(fun(x, y, m, 0));

    }
    private static int fun(int x, int y, int m,int count) {
        if (x>=m||y>=m)
            return count;
        else if (x==0||y==0||(x<0&&y<0))
            return -1;
        else {
            int temp = x+y;
            if (temp>Math.max(x,y)){
                y = temp;
                x = Math.max(x,y);
            }else {
                x = temp;
                y = Math.max(x,y);
            }
            count++;
            int fun1 = fun(x, temp, m, count);
            int fun2 = fun(temp, y, m, count);
            if (fun1==-1||fun2==-1) return Math.max(fun1,fun2);
            else return Math.min(fun1,fun2);
        }
    }
}
